This invention relates to injection blow molding apparatus, and more particularly, to an injection blow molding apparatus including stacked molds.
Various processes are used in injection molding of hollow plastic articles, and typically processes which have overlapping time cycles in order to reduce production time. One method for producing hollow plastic articles, which is commonly referred to as the Farkus method, employs vertically oriented back-to-back injection molds and blow molds. Examples of this type of injection blow molding apparatus are disclosed in U.S. Pat. Nos. 4,540,543 and 4 604,258. The apparatus includes a pair of blow molds which are arranged above and below a single cavity injection mold in a vertical plane, so that while one preform is being molded, another is being blown. Shuttle plates move the preforms vertically from the injection mold to the blow molds and from the blow molds to an ejection apparatus. The use of vertically oriented back-to-back injection and blow molds doubles the output without appreciably increasing the size of the injection blow molding apparatus. However, this type of apparatus lacks sufficient space for ejecting completed products.
Most commercial injection blow molding machines incorporate a common type of Gussoni horizontal indexing mechanism. The Gussoni apparatus includes three or more stations which are arranged in a loop, and the process moves in sequence from station to station until it reaches the initial station, and then the process is repeated. The first station, which is the preform station, includes a preform injection mold, typically having a plurality of mold cavities so that a plurality of preforms can be produced simultaneously. The second station, which is the blow station, includes a blow mold having the same number of blow mold cavities as the preform mold for blowing the preforms into hollow articles. The third station, which is the eject station, includes apparatus for ejecting the hollow articles from the apparatus. The apparatus further includes a plurality of sets of cores which are mounted on a rotating indexing head which rotates in a horizontal plane. The cores cooperate with the molds in producing the articles and move the articles from station to station during the blow molding process.
In the initial stage of the process at the preform station, one set of cores is moved into the cavities of the preform injection mold and the mold is closed and clamped. Then, hot plastic resin is injected through a nozzle into a manifold though individual nozzle tips into the cavities of the preform mold where the exact amount of material needed to form the preforms is injected around cores located in the cavities. Then, the preform mold opens and the indexing head indexes the cores carrying the injected preforms 120.degree. to the blow mold at the second station. The blow mold closes and the preforms are blown by air to the final shape of the containers. Then, the blow mold opens and the indexing head again indexes the cores carrying the finished containers 120.degree. to the eject station where the containers are ejected by a stripper bar either directly off the cores or into a transfer unit for orientation on a conveyor. In this type of equipment, one preform is being molded at the preform station while another is being blown at the blow station and a formed container is being removed from the apparatus at the eject station. This apparatus provides a simple way for ejecting the finished from the apparatus but is limited by in the number of product that can be produced at the same time.